Conventionally, taste determination and taste evaluation of beverages, foods, and oral drugs are carried out by sensory evaluation methods using human gustatory sensation. In Taste Dilution Analysis, which is one of such sensory evaluation methods, a plurality of subjects (or panelists) evaluate the taste of a sample to be analyzed by diluting the sample in small steps, and determine the last remaining taste after a significant diluting step. However, since the evaluations vary between panelists and vary due to the panelist's daily physical condition and emotional feelings, it may be difficult to obtain objective and reproducible evaluations even if the test is carried out by more than one panelist. In addition, it is difficult to ensure or foster panelists because a panelist is required to take constant control of his/her own health care.
Meanwhile, it is essential to evaluate tastes when developing food or drink products or when practicing quality control of a manufacturing line. Therefore, an apparatus comparable to the human sense of taste which can evaluate taste is earnestly desired. At the same time, such taste sensing systems as disclosed in Patent Document 1 and Non-Patent Document 1 for example are conventionally known. It is known that an interaction between the lipid membrane (polymer membrane) and a chemical substance to be analyzed causes potential difference changes between a lipid membrane electrode and a standard reference electrode. Using this potential difference, such taste sensing systems evaluate the taste of a sample to be analyzed.
Specifically, the system disclosed in Patent Document 1 comprises eight taste sensors which measure potential differences using plural lipid membranes, and analyze the tastes by performing a principal component analysis or multiple linear regression analysis of the detection output from each sensor. At present, five tastes, namely, saltiness, sourness, umami (savoriness), bitterness, and astringency can be analyzed in practical use. The eight taste sensors are divided into two sensor groups of four sensors according to their characteristics.
The system proceeds an analysis in line with the following steps:    (1) Bring the taste sensors belonging to each sensor group into contact with a reference solution in a container which is the basis of the signal outputs, and wait until the signal output from each taste sensor is stabilized.    (2) Bring the taste sensors belonging to each sensor group into contact with a liquid sample to be analyzed in a container, and monitor the changes of each signal output.    (3) Run a principal component analysis (or multiple linear regression analysis) program to the monitored signals and determine the taste.    (4) Once again bring the taste sensors belonging to each sensor group into contact with a reference solution in a container, wait until the signal output from the taste sensors are stabilized, and confirm that the signal level returns to the level before monitoring (i.e. the signal level in step (1)).    (5) If, in step (4), the signal level does not return to the level before monitoring, cleanse each taste sensor with cleaning fluid.
Such a conventional taste sensing system is designed to evaluate the comprehensive taste or tastes of a whole sample to be analyzed, and a variety of test results are made public. However, since such previous taste sensing systems cannot capture individual tastes of various substances included in a sample, it is not possible to study what kind of substance contributes to the overall taste of the sample, or investigate the relationship between the combination of the taste of each substance and the overall taste.
In addition, a condition being that, when plural tastes are mixed, a certain taste changes in the human sense or inversely does not change in the human sense but causes change of a measurement value is conventionally known. Quinine, for example, known as an antimalarial drug, has an intense bitter taste, but if a sweet component such as sucrose is added to it, the measured bitter taste value is reduced although the bitter taste is not reduced in the human sense (see Non-Patent Document 2). Like this example, when studying how the taste changes depending on the presence or absence of an additive with the conventional taste sensing system, unfortunately it takes much time and effort to analyze: it is required to prepare both a sample with an additive and a sample without an additive, and then perform the analyses independently.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. H3-163351
[Non-Patent Document 1] “Products, Taste Sensing System : SA402B”, which is disclosed in the Website of Intelligent Sensor Technology, Inc.
[Non-Patent Document 2] “KANSEI BIOSENSOR TO IT SHAKAI”, IEEJ Transactions on Sensors and Micromachines, Vol. 124, No. 7, 2004, pp. 229-232.
To solve the above-described problem, the present invention intends to provide a taste analyzing apparatus for obtaining detailed knowledge such as a relationship between the overall taste of a sample and the taste of each of the various components contained in the sample, by measuring the individual taste of the various components contained in the sample minutely and objectively.